Stretchable polymer thick film compositions for thermoplastic substrates and wearables electronics

ABSTRACT

This invention is directed to stretchable polymer thick film compositions useful for wearable garments. More specifically, the polymer thick film may be used in applications where significant stretching is required, particularly on substrates that can be highly elongated. A particular type of substrate is a thermoplastic polyurethane substrate.

FIELD OF THE INVENTION

This invention is directed to polymer thick film compositions. Morespecifically, the polymer thick film composition may be used inapplications where significant stretching is required, particularly onsubstrates that can be highly elongated. A particular type of substratewhich is suitable is a thermoplastic polyurethane (TPU) substrate thatcan be used in wearable garments applications. Another approach utilizesprinting directly onto the fabric alone, either containing conductivefiller like carbon or silver, or without conductive filler, either wovenor knit, to produce stretchable conductive traces and sensors.

BACKGROUND OF THE INVENTION

Conductive polymer thick film (PTF) circuits have long been used aselectrical elements. Although they have been used as electricalelements, the use of PTF silver conductors in highly stretchableapplications such as for wearable garments is not common. The ability tobe stretched and exposed to multiple wash and dry cycles and stillmaintain conductivity is critical. Additionally, one typical substrateused for this type of application is a thermoplastic polyurethanesubstrate (TPU substrate), and the PTF compositions must be compatiblewith this substrate. One of the purposes of this invention is to addressthe above requirements and produce a series of stretchable PTF inks thatcan be used in the construction of a functional circuit to be used on asubstrate which may be used as a wearable garment or which can beapplied to a fabric which may be used as a wearable garment.

SUMMARY OF THE INVENTION

This invention provides a polymer thick film composition comprising:

-   -   (a) a functional component; and    -   (b) an organic medium comprising 5-50 wt % thermoplastic        polyurethane resin dissolved in an organic solvent, the        thermoplastic polyurethane having a percent elongation of at        least 200% and a tensile stress necessary to achieve 100%        elongation of less than 1000 psi, wherein the weight percent is        based on the total weight of the organic medium.

The choice of the functional component determines the properties of thecomposition and the kind of polymer thick film that can be formed fromthe composition.

In one embodiment, the functional component is an electricallyconductive powder and the invention provides a polymer thick filmconductor composition comprising:

-   -   (a) an electrically conductive metal powder, wherein the metal        is selected from the group consisting of Ag, Cu, Au, Pd, Pt, Sn,        Al, Ni, an alloy of Ag, Cu, Au, Pd, Pt, Sn, Al, Ni and mixtures        thereof; and    -   (b) an organic medium comprising 5-50 wt % thermoplastic        polyurethane resin dissolved in an organic solvent, the        thermoplastic polyurethane having a percent elongation of at        least 200% and a tensile stress necessary to achieve 100%        elongation of less than 1000 psi, wherein the weight percent is        based on the total weight of the organic medium.

In another embodiment, the functional component is silver powder incombination with silver chloride powder and the invention provides apolymer thick film conductor composition comprising:

-   -   (a) silver powder in combination with silver chloride powder;        and    -   (b) an organic medium comprising 5-50 wt % thermoplastic        polyurethane resin dissolved in an organic solvent, the        thermoplastic polyurethane having a percent elongation of at        least 200% and a tensile stress necessary to achieve 100%        elongation of less than 1000 psi, wherein the weight percent is        based on the total weight of the organic medium.

In yet another embodiment, the functional component is graphite,conductive carbon or a mixture thereof and the invention provides apolymer thick film overcoat composition comprising:

-   -   (a) graphite, conductive carbon or a mixture thereof; and    -   (b) an organic medium comprising 5-50 wt % thermoplastic        polyurethane resin with a % elongation of at least 200%        dissolved in an organic solvent, wherein the weight percent is        based on the total weight of the organic medium.

In still another embodiment, the functional component is fumed silicaand the invention provides a polymer thick film encapsulant compositioncomprising:

-   -   (a) fumed silica; and    -   (b) an organic medium comprising 5-50 wt % thermoplastic        polyurethane resin with a % elongation of at least 200%        dissolved in an organic solvent, wherein the weight percent is        based on the total weight of the organic medium.

The invention is further directed to using the highly stretchablecompositions to form conductive electrical circuits and overcoats andencapsulants to protect these circuits on substrates for wearablegarments.

DETAILED DESCRIPTION OF INVENTION

The invention relates to polymer thick film compositions for use inelectrical circuits and, in particular, highly stretchable deformedcircuits such as those applications where functional circuitry isgenerated on fabrics for clothing. This is often referred to aswearables electronics. A layer of conductor is printed and dried on asubstrate so as to produce a functioning circuit and then the entirecircuit is subjected to the typical bending/creasing that a fabric wouldreceive. Additionally, as is typical for fabrics, they must be washedand dried on a periodic basis and the conductivity and integrity of theconductor must be maintained.

The substrates commonly used in polymer thick film circuits arepolyester (PET), polycarbonate and others. However, those cannot be usedhere. However, it has been found that one particular class ofsubstrates, thermoplastic polyurethane substrates (TPU's), along withthe series of polymer thick film compositions disclosed herein producestretchable circuits that can be used in making wearable electronics inwashable garments.

In some embodiments, the electrically conductive metal powder of thepolymer thick film (PTF) conductor composition is comprised of (i)silver flakes, or silver flakes and silver chloride powder or graphite,conductive carbon or mixtures thereof and (ii) an organic mediumcomprising a polymer resin dissolved in an organic solvent. When theelectrically conductive metal powder is replaced by fumed silica, thePTF composition serves as an encapsulant. Additionally, other powdersand printing aids may be added to improve the composition.

Herein weight percent is written as wt %.

Conductor Compositions

When the functional component is an electrically conducting material,the composition can be used to form an electrical conductor.

In one embodiment the electrically conductive metal powder is a powderof electrically conductive metal particles. The. electrically conductivemetal is selected from the group consisting of Ag, Cu, Au, Pd, Pt, Sn,Al, Ni, an alloy of Ag, Cu, Au, Pd, Pt, Sn, Al, Ni and mixtures thereof.In an embodiment, the conductive particles include silver (Ag). In afurther embodiment, the conductive particles may, for example, includeone or more of the following: Ag, Cu, Au, Pd, Pt, Sn, Al, Ni, Ag—Pd andPt—Au. In another embodiment, the conductive particles include one ormore of the following: (1) Al, Cu, Au, Ag, Pd and Pt; (2) an alloy ofAl, Cu, Au, Ag, Pd and Pt; and (3) mixtures thereof. In still anotherembodiment, the conductive particles include one of the above mentionedmetals coated with another of the metals, e.g., Ag-coated Cu,Ag-coated-Ni. An embodiment contains a mixture of any of the above.

In one such embodiment, the electrically conductive powders in thepresent thick film composition are silver powders and may comprisesilver metal powder, alloys of silver metal powder, or mixtures thereof.Various particle diameters and shapes of the conductive powder arecontemplated. In an embodiment, the conductive powder may include anyshape silver powder, including spherical particles, flakes (rods, cones,plates), and mixtures thereof. In one embodiment, the conductive powderis in the form of silver flakes.

In an embodiment, the particle size distribution of the conductivepowders may be 1 to 100 microns; in a further embodiment, 2-10 microns.

In an embodiment, the surface area/weight ratio of the silver particlesmay be in the range of 0.1-1.0 m²/g.

Furthermore, it is known that small amounts of other metals may be addedto silver conductor compositions to improve the properties of theconductor. Some examples of such metals include: gold, copper, nickel,aluminum, platinum, palladium, molybdenum, tungsten, tantalum, tin,indium, lanthanum, gadolinium, boron, ruthenium, cobalt, titanium,yttrium, europium, gallium, sulfur, zinc, silicon, magnesium, barium,cerium, strontium, lead, antimony, conductive carbon, and combinationsthereof and others common in the art of thick film compositions. Theadditional metal(s) may comprise up to about 1.0 percent by weight ofthe total composition.

In various embodiments, the electrically conductive metal powder may bepresent at 20 to 92 wt %, 30 to 70 wt %, or 45 to 65 wt % based on thetotal weight of the composition.

In another conductor embodiment, the functional component is silverpowder in combination with silver chloride powder. This combination ispresent at 20 to 92 wt %, based on the total weight of the composition.The ratio of the weight of the silver powder to the weight of the silverchloride powder is in the range of 9 to 1 to 0.1 to 1. In one embodimentthe silver powder is in the form of silver flakes.

The functional powder may consist of graphite, conductive carbon ormixtures and the resulting composition can be used as a protective inkto form an overcoat. The amount of graphite, conductive carbon ormixtures may be present at 20 to 92 wt %, based on the total weight ofthe composition.

Organic Medium

The organic medium is comprised of a thermoplastic polyurethane resindissolved in an organic solvent. The polyurethane resin must achievegood adhesion to an underlying substrate. The polyurethane resin must becompatible with and not adversely affect the performance of the circuitafter deformation and wash and dry cycles.

In one embodiment the thermoplastic polyurethane resin is 5-50 wt % ofthe total weight of the organic medium. In another embodiment thethermoplastic polyurethane resin is 20-45 wt % of the total weight ofthe organic medium and in still another embodiment the thermoplasticpolyurethane resin is 23-30 wt % of the total weight of the organicmedium. In an embodiment the thermoplastic polyurethane resin is apolyurethane homopolymer. In another embodiment the polyurethane resinis a polyester-based copolymer. In one embodiment the thermoplasticpolyurethane resin is a predominantly linear hydroxyl polyurethane.

The thermoplastic polyurethane resin has a % elongation of at least200%.

Percent elongation is defined in the usual way:

${{Percent}\mspace{14mu} {Elongation}} = {\frac{{{Final}\mspace{14mu} {Length}} - {{Initial}\mspace{14mu} {Length}}}{{Initial}\mspace{14mu} {Length}} \times 100}$

The thermoplastic polyurethane resin also has a tensile stress necessaryto achieve 100% elongation of less than 1000 pounds per square inch(psi).

The polymer resin is typically added to the organic solvent bymechanical mixing to form the medium. Solvents suitable for use in thepolymer thick film composition are recognized by one of skill in the artand include acetates and terpenes such as carbitol acetate and alpha- orbeta-terpineol or mixtures thereof with other solvents such as kerosene,dibutylphthalate, butyl carbitol, butyl carbitol acetate, hexyleneglycol and high boiling alcohols and alcohol esters. In addition,volatile liquids for promoting rapid hardening after application on thesubstrate may be included. In many embodiments of the present invention,solvents such as glycol ethers, ketones, esters and other solvents oflike boiling points (in the range of 180° C. to 250° C.), and mixturesthereof may be used. Various combinations of these and other solventsare formulated to obtain the viscosity and volatility requirementsdesired. The solvents used must solubilize the resin. Solvent may beadded to the composition to adjust the viscosity and may be consideredpart of the organic medium.

In various embodiments, the organic medium may be present at 8 to 80 wt%, 30 to 70 wt %, or 35 to 55 wt % based on the total weight of thecomposition.

Overcoat Composition

A particular conductor version of the compositions of the invention maybe formulated to be used as an overcoat to protect the conductor formedfrom the polymer thick film conductor compositions discussed above. fromthe harsh environment of the wash and dry cycles. The polymer thick filmovercoat composition is formulated by using graphite, conductive carbonor a mixture thereof and the organic medium mentioned above. Theovercoat results in a minimal shift in resistance of the conductor withwash and dry cycles.

Encapsulant Composition

A non-conductor version of the compositions of the invention may also beformulated. This type of encapsulant or dielectric is very useful inthat it protects the conductors from the harsh environment of the washand dry cycles. The composition may be directly deposited onto theconductor or be applied over an overcoat layer. This composition isformulated by using only the organic medium mentioned above with theaddition of fumed silica as a powder and/or the addition of a dye asneeded. The amount of fumed silica used is from 0.1 to 3 wt % and theamount of organic medium is from 97 to 99.9 wt %, based on the totalweight of the composition. In one embodiment, the amount of fumed silicaused is from 0.5 to 1.5 wt % and the amount of organic medium is from98.5 to 99.5 wt %, based on the total weight of the composition.

Additional Powders

Various powders or additives may be added to the PTF compositions toimprove adhesion, modify the rheology and increase the low shearviscosity thereby improving the printability.

Application of the PTF Compositions

The PTF compositions, also referred to as “pastes”, are deposited on asubstrate which may be used as a wearable garment or which can beapplied to a fabric which may be used as a wearable garment. Onesubstrate is a thermoplastic polyurethane substrate, such as BemisST-604 available from Bemis Associates, Inc., Shirley, Mass. Anotherpossible substrate is a thermoplastic polyester, such as Hytrel®available from the DuPont Co., Wilmington, Del. The substrate can alsobe a sheet of a composite material made up of a combination of plasticsheet with a permeable coating deposited thereupon.

The deposition of the PTF compositions on the substrate are performedtypically by screen printing, but other deposition techniques such asstencil printing, syringe dispensing or coating techniques can beutilized. In the case of screen-printing, the screen mesh size controlsthe thickness of the deposited thick film.

Generally, a thick film composition comprises a functional phase thatimparts appropriate functional properties to the composition. Forexample, the functional phase may comprise electrically functionalpowders dispersed in an organic medium that acts as a carrier for thefunctional phase. Generally, the composition is fired to burn out boththe polymer and the solvent of the organic medium and to impart theelectrically functional properties. However, in the case of a polymerthick film composition, the polymer portion of the organic mediumremains as an integral part of the composition after drying.

The PTF compositions are processed for a time and at a temperaturenecessary to remove all solvent. For example, the deposited thick filmis dried by exposure to heat at 130° C. for typically 10-15 min.

Circuit Construction

The base substrate used is typically 5 mil thick TPU. The conductorcomposition is printed and dried as per the conditions described above.One or more layers of the conductor PTF composition can be printed anddried on the substrate and a protective overcoat and/or protectiveencapsulant layer can be applied over the dried conductor PTFcomposition and dried. In one embodiment the conductor is covered by anovercoat layer formed from the polymer thick film overcoat compositionof the invention. In another embodiment the conductor is covered by anencapsulant layer formed from the polymer thick film encapsulantcomposition of the invention. In still another embodiment the conductoris covered by an overcoat layer formed from the polymer thick filmovercoat composition of the invention which is then covered by anencapsulant layer formed from the polymer thick film encapsulantcomposition of the invention.

The base substrate may be used directly as a wearable garment.Alternatively, the substrate may be applied to a fabric which can beused to form a wearable garment. Either side of the substrate may beapplied to the fabric, i.e., the side of the substrate with theconductor can be adjacent to the fabric or the other side of thesubstrate may be adjacent to the fabric. A thermoplastic polyurethanesubstrate, such as Bemis ST-604, adheres to polyurethane or polyvinylchloride coated fabrics,

In another embodiment the conductor composition may be applied directlyto a stretchable permeable fabric. One such non-woven fabric is oneconstructed from Evolon® available from Fruedenberg Evolon, Colmar,France. Another permeable substrate that may be used for this type ofapplication is a woven polyester coated with polyamide, e.g., Cetus®OS5000U available from Dynic Corp, Kyoto, Japan.

The depositions of the PTF compositions can be applied to a TPU film,then laminated to a fabric structure, or printed directly onto a fabric,containing conductive filler in the fiber or onto knit, woven, ornonwoven fabric constructions. In the instance of printing directly onthe fabric conductive ink systems can be in the form of screen-printing,or other non-contact method such as aerosol, extrusion printing, orinjet. A typical process would be to apply an insulating layer ofthermoplastic, UV, or combination of both to act as a base layer toprevent subsequent layers of conductive inks such as silver or carbonfrom bleeding through or interacting electrically with a conductivefabric structure. The next prints would be the conductive inks, followedby insulating thermoplastic, UV, or combination of insulators includinga top layer of TPU adhesive or moisture barrier film.

EXAMPLES AND COMPARATIVE EXPERIMENTS Example 1

The PTF conductor composition was prepared in the following manner. 40.0parts by weight of an organic medium was used and was prepared by mixing28.5 wt % Desmocoll® 406 polyurethane (Bayer Material Science LLC,Pittsburgh, Pa.) with 71.5 wt % Dowanol™ DPM glycol ether (obtained fromDow Co., Midland Mich.) organic solvent. The molecular weight of theresin was approximately 20,000. This mixture was heated at 90° C. for1-2 hours to dissolve all the resin. 60.00 parts by weight of a flakesilver powder with an average particle size of approximately 5 micronswas added. Finally, approximately 12.75 parts by weight of the Dowanol™DPM glycol ether was added for thinning purposes to bring thecomposition to a desired viscosity.

This composition was mixed for 30 minutes on a planetary mixer, and thensubjected to several passes on a three roll-mill.

A circuit was then fabricated as follows. On a 5 mil thick Bemis ST-604TPU substrate, a pattern of a series of interdigitated composition lineswere printed using a 280 mesh stainless steel screen. The patternedlines were dried at 130° C. for 10 min. in a forced air box oven. Anormalized resistivity of 50 mohm/sq/mil was observed. The pattern wassubjected to 50 wash and dry cycles (40° C. wash temperature).Resistance was measured before and after the 50 wash and dry cycles todetermine the change. The resistance change is shown in Table 1.

Example 2

A circuit was produced as described in Example 1. The only differencewas that an encapsulant layer of the invention was printed and dried ontop of the conductive composition. The encapsulant composition used toform the encapsulant layer was comprised of 1 wt % fumed silica and 99wt % organic medium identical to that used in Example 1, wherein the wt% are based on the total weight of the composition. Resistance wasmeasured before and after the 50 wash and dry cycles to determine thechange. The resistance change is shown in Table 1.

Comparative Experiment A

A circuit was produced as described in Example 1. The only differencewas that the conductor composition contained two different resins,polyurethane and hydroxyl ether with lower % elongation than thepolyurethane resin used in Example 1. Resistance was measured before andafter the 50 wash and dry cycles to determine the change. The resistancechange is shown in Table 1.

TABLE 1 Resistance Change Sample after 50 Wash/Dry Cycles Example 1   1ohm Example 2 0.5 ohm Comparative Exp. A   6 ohm

The results show the strikingly better results obtained in Examples 1and 2 compared with Comparative Example A due to the use of thethermoplastic polyurethane resin. The use of the encapsulant furtherimproves the performance (lower resistance change) compared to Example 1and thus supports the use of these compositions for practical wearablesapplications such as functional clothing.

Example 3

A PTF conductor composition was prepared using Desmocoll® 406polyurethane (Bayer Material Science LLC, Pittsburgh, Pa.) essentiallyas described in Example 1. The Desmocoll® 406 has a tensile stressnecessary to achieve 100% elongation of 420 psi. A circuit wasfabricated as follows. On a black TPU film, a pattern of a series ofinterdigitated composition lines were printed using a 230 mesh, 1.4 milstainless steel screen. The printed lines were dried at 120° C. for 15minutes. A track of the film 10 cm long and 1 cm wide was then stretchedto an elongation of 15%. The initial resistance was 5 ohms and theresistance after the 15% elongation was 45 ohms for an increase of 40ohms.

Example 4

A circuit was prepared and the resistance was measured essentially asdescribed in Example 3. The only difference was that the polyurethaneresin used in the PTF conductor composition was Desmocoll® 176polyurethane (Bayer Material Science LLC, Pittsburgh, Pa.). TheDesmocoll® 176 has a tensile stress necessary to achieve 100% elongationof 330 psi. The resistance increase after the 15% elongation was 12ohms.

Example 5

A circuit was prepared and the resistance was measured essentially asdescribed in Example 3. The only difference was that the polyurethaneresin used in the PTF conductor composition was Desmocoll® 526polyurethane (Bayer Material Science LLC, Pittsburgh, Pa.). TheDesmocoll® 526 has a tensile stress necessary to achieve 100% elongationof 650 psi. The resistance increase after the 15% elongation was 13ohms.

Comparative Experiment B

A circuit was prepared and the resistance was measured essentially asdescribed in Example 3. The only difference was that the polyurethaneresin used in the PTF conductor composition was Desmocoll® 530polyurethane (Bayer Material Science LLC, Pittsburgh, Pa.). TheDesmocoll® 530 has a tensile stress necessary to achieve 100% elongationof 1200 psi. The resistance increase after the 15% elongation was 75ohms.

The resistance increases after a 15% elongation for Examples 3-5 andComparative Experiment B are summarized in Table 2

TABLE 2 Stress for Resistance Sample 15% Elongation Change Example 3 420psi 40 ohms Example 4 330 psi 12 ohms Example 5 650 psi 13 ohmsComparative Exp. B 1200 psi  75 ohms

Example 6

A composition was prepared as described in Example 1 with the exceptionthat the conductive metal powder was composed of silver flake powder andsilver chloride powder, obtained from Colonial Metals Company, Columbia,Pa. The average size of the silver chloride powder particles was 15microns. The wt % of each component was:

Silver flake 44.07 Silver chloride powder 23.73 Oreganic medium 16.95Dowanol ™ DPM glycol ether 15.25

A circuit was fabricated as described in Example 1 and was usedsuccessfully as an electrode in a wearables application.

What is claimed is:
 1. An article containing an electrical circuitcomprising an element formed from a polymer thick film compositioncomprising: (a) a functional component; and (b) an organic mediumcomprising 5-50 wt % thermoplastic polyurethane resin dissolved in anorganic solvent, said thermoplastic polyurethane resin having a percentelongation of at least 200% and a tensile stress necessary to achieve100% elongation of less than 1000 psi, wherein the weight percent isbased on the total weight of said organic medium; wherein saidcomposition is dried to remove said solvent and form said element. 2.The article of claim 1, wherein said element is a conductor and whereinsaid functional component is an electrical conductive metal powder andsaid polymer thick film composition is a polymer thick film conductorcomposition comprising: (a) an electrically conductive metal powder,wherein said metal is selected from the group consisting of Ag, Cu, Au,Pd, Pt, Sn, Al, Ni, an alloy of Ag, Cu, Au, Pd, Pt, Sn, Al, Ni andmixtures thereof; and (b) an organic medium comprising 5-50 wt %thermoplastic polyurethane resin dissolved in an organic solvent, saidthermoplastic polyurethane resin having a percent elongation of at least200% and a tensile stress necessary to achieve 100% elongation of lessthan 1000 psi, wherein the weight percent is based on the total weightof said organic medium; wherein said composition is dried to remove saidsolvent and form said conductor.
 3. The article of claim 2, wherein saidelectrically conductive metal powder is silver powder.
 4. The article ofclaim 3, wherein said silver powder is in the form of silver flakes andwherein said thermoplastic polyurethane resin is selected from the groupconsisting of a polyester-based polymer, a urethane homopolymer and apredominantly linear hydroxyl polyurethane.
 5. The article of claim 2,said polymer thick film conductor composition comprising 20 to 92 wt %electrically conductive metal powder and 8 to 80 wt % organic medium,wherein the wt % are based on the total weight of said composition. 6.The article of claim 1, wherein said element is a conductor and whereinsaid functional component is silver powder in combination with silverchloride powder and said polymer thick film composition is a polymerthick film conductor composition comprising: (a) silver powder incombination with silver chloride powder; and (b) an organic mediumcomprising 5-50 wt % thermoplastic polyurethane resin dissolved in anorganic solvent, said thermoplastic polyurethane resin having a percentelongation of at least 200% and a tensile stress necessary to achieve100% elongation of less than 1000 psi, wherein the weight percent isbased on the total weight of said organic medium; wherein saidcomposition is dried to remove said solvent and form said conductor. 7.The article of claim 6, wherein said silver powder is in the form ofsilver flakes and wherein said thermoplastic polyurethane resin isselected from the group consisting of a polyester-based polymer, aurethane homopolymer and a predominantly linear hydroxyl polyurethane.8. The article of claim 7, said polymer thick film conductor compositioncomprising 20 to 92 wt % silver flakes in combination with silverchloride powder and 8 to 80 wt % organic medium, wherein the wt % arebased on the total weight of said composition.
 9. The article of claim1, wherein said element is a conductor and wherein said functionalcomponent is graphite, conductive carbon or a mixture thereof and saidpolymer thick film composition is a polymer thick film conductorcomposition comprising: (a) graphite, conductive carbon or a mixturethereof; and (b) an organic medium comprising 5-50 wt % thermoplasticpolyurethane resin dissolved in an organic solvent, said thermoplasticpolyurethane resin having a percent elongation of at least 200% and atensile stress necessary to achieve 100% elongation of less than 1000psi, wherein the weight percent is based on the total weight of saidorganic medium; wherein said composition is dried to remove said solventand form said conductor.
 10. The polymer thick film composition of claim9, said polymer thick film conductor composition comprising 20 to 92 wt% graphite, conductive carbon or a mixture thereof and 8 to 80 wt %organic medium, wherein the wt % are based on the total weight of saidcomposition and wherein said thermoplastic polyurethane resin isselected from the group consisting of a polyester-based polymer, aurethane homopolymer and a predominantly linear hydroxyl polyurethane.11. The article of claim 1, wherein said element is an encapsulant andwherein said functional component is fumed silica and said polymer thickfilm composition is a polymer thick film encapsulant compositioncomprising: (a) fumed silica; and (b) an organic medium comprising 5-50wt % thermoplastic polyurethane resin dissolved in an organic solvent,said thermoplastic polyurethane resin having a percent elongation of atleast 200% and a tensile stress necessary to achieve 100% elongation ofless than 1000 psi, wherein the weight percent is based on the totalweight of said organic medium; wherein said composition is dried toremove said solvent and form said encapsulant.
 12. The article of claim11, said polymer thick film encapsulant composition comprising 0.1 to 3wt % fumed silica and 97 to 99.9 wt % organic medium, wherein the wt %are based on the total weight of said composition and wherein saidthermoplastic polyurethane resin is selected from the group consistingof a polyester-based polymer, a urethane homopolymer and a predominantlylinear hydroxyl polyurethane.
 13. The article of claim 2, wherein saidconductor is covered by an overcoat layer formed from a polymer thickfilm carbon composition comprising: (a) graphite, conductive carbon or amixture thereof; and (b) an organic medium comprising 5-50 wt %thermoplastic resin dissolved in an organic solvent, said thermoplasticpolyurethane resin having a percent elongation of at least 200% and atensile stress necessary to achieve 100% elongation of less than 1000psi, wherein the weight percent is based on the total weight of saidorganic medium; wherein said composition is dried to remove said solventand form said overcoat layer.
 14. The article of claim 6, wherein saidconductor is covered by an overcoat layer formed from a polymer thickfilm carbon composition comprising: (a) graphite, conductive carbon or amixture thereof; and (b) an organic medium comprising 5-50 wt %thermoplastic resin dissolved in an organic solvent, said thermoplasticpolyurethane resin having a percent elongation of at least 200% and atensile stress necessary to achieve 100% elongation of less than 1000psi, wherein the weight percent is based on the total weight of saidorganic medium; wherein said composition is dried to remove said solventand form said overcoat layer.
 15. The article of claim 2, wherein saidconductor is covered by an encapsulant layer formed from a polymer thickfilm encapsulant composition comprising: (a) fumed silica; and (b) anorganic medium comprising 5-50 wt % thermoplastic polyurethane resindissolved in an organic solvent, said thermoplastic polyurethane resinhaving a percent elongation of at least 200% and a tensile stressnecessary to achieve 100% elongation of less than 1000 psi, wherein theweight percent is based on the total weight of said organic medium;wherein said composition is dried to remove said solvent and form saidencapsulant layer.
 16. The article of claim 6, wherein said conductor iscovered by an encapsulant layer formed from a polymer thick filmencapsulant composition comprising: (a) fumed silica; and (b) an organicmedium comprising 5-50 wt % thermoplastic polyurethane resin dissolvedin an organic solvent, said thermoplastic polyurethane resin having apercent elongation of at least 200% and a tensile stress necessary toachieve 100% elongation of less than 1000 psi, wherein the weightpercent is based on the total weight of said organic medium; whereinsaid composition is dried to remove said solvent and form saidencapsulant layer.
 17. The article of claim 9, wherein said conductor iscovered by an encapsulant layer formed from a polymer thick filmencapsulant composition comprising: (a) fumed silica; and (b) an organicmedium comprising 5-50 wt % thermoplastic polyurethane resin dissolvedin an organic solvent, said thermoplastic polyurethane resin having apercent elongation of at least 200% and a tensile stress necessary toachieve 100% elongation of less than 1000 psi, wherein the weightpercent is based on the total weight of said organic medium; whereinsaid composition is dried to remove said solvent and form saidencapsulant layer.
 18. The article of claim 13, wherein said overcoatlayer is covered by an encapsulant layer formed from a polymer thickfilm encapsulant composition comprising: (a) fumed silica; and (b) anorganic medium comprising 5-50 wt % thermoplastic polyurethane resindissolved in an organic solvent, said thermoplastic polyurethane resinhaving a percent elongation of at least 200% and a tensile stressnecessary to achieve 100% elongation of less than 1000 psi, wherein theweight percent is based on the total weight of said organic medium;wherein said composition is dried to remove said solvent and form saidencapsulant layer.
 19. The article of claim 14, wherein said overcoatlayer is covered by an encapsulant layer formed from a polymer thickfilm encapsulant composition comprising: (a) fumed silica; and (b) anorganic medium comprising 5-50 wt % thermoplastic polyurethane resindissolved in an organic solvent, said thermoplastic polyurethane resinhaving a percent elongation of at least 200% and a tensile stressnecessary to achieve 100% elongation of less than 1000 psi, wherein theweight percent is based on the total weight of said organic medium;wherein said composition is dried to remove said solvent and form saidencapsulant layer.
 20. The article as in any one of the precedingclaims, wherein the article is a wearable garment.